Process and System for Removing Printing in Metallic Packages

ABSTRACT

Process and system for removing printing in metallic packages used in drinks, food and other applications in general, comprising the removal of ink before the cure thereof, by means of spray with ink remover liquid and non abrasive friction. Preferably, said liquid is an alkaline aqueous solution, which is sprayed onto the package surface simultaneously with the friction thereof with a soft and non abrasive element. In a preferred embodiment, said friction results in the rotation of the package around the longitudinal axis thereof, which is mounted on a rotative support, and the soft non abrasive element in contact with the surface thereof keeps motionless.

FIELD OF THE INVENTION

The present invention refers to the cleansing of metallic cans on which body there are printed labels and, more particularly, to the conditioning cans for food, drinks and other applications in general.

BACKGROUND OF THE INVENTION

The increasing technological development stimulates and challenges the evolutive progress of society, thus enlarging the capacity of storage, processing and transformation of the information into knowledge. Such fact is observed in view of the necessity of innovating whenever we face a certain obstacle and/or problem, it requiring an effective solution which unites rapidity, objectivity, productivity and an excellent cost/benefit relation.

The use of metallic packages for the conditioning of various products is generalized practice, specially in relation to the packages of food, drinks and other applications in general that are retailed. These packages shall have a distinctive look presentation in order to attract the consumer's attention, helping him, at the same time, in the selection of the desired product. The resource nowadays adopted to reach such objectives consists of printing labels in several colors, directly on the metallic surface of these packages. Therefore, there were developed inks and automatized specific processes, which allow a production volume of the order of million of units per day.

Such printing techniques present satisfactory results in almost all cases. However, the high production volume—which, in the case of drink cans, can reach 6 million units per day—causes even a relatively low percentage of inappropriate printings to result in a considerable volume of waste, in absolute terms. Upon considering the losses that occur during the adjustment of the printing equipment, the number of rejected units is of the order of 1,000,000 per month.

Upon considering that, in the case of the drink cans, the body weighs about 12 grams, the waste estimate can reach 18 tons per month of aluminum, of which recycling is imposed due to the value of this metal. Traditionally, this recycling has been carried out by returning the cans as scrap to the aluminum works, wherein the material is casted and reused. Nevertheless, the casting process consumes electric energy which can be harmful to environment. From the point of view of the industries that produce these packages, it is further necessary to consider the charges arising from the administrative expenses and the material conveying costs.

The removal of the ink from the cans is, therefore, a recommendable alternative, it making the operation of the industries involved in the process more profitable. However, the removal by organic solvents presents a negative impact to the environment, and it can cause penalties such as fine up to a possible interdiction of the operations. On the other hand, the printing process requires the application of the ink onto a flat surface, thereby making impracticable the techniques of ink removal by means of abrasion.

OBJECTIVES OF THE INVENTION

In view of what has been set forth, the present invention aims to provide printing removal means in packages, which avoid the necessity of casting thereof to the reuse of the metal.

It is another objective of the invention the provision of means which, besides making the efficient printing removal, keep the structure and the surface finishing thereof intact so as to allow the releading to the production line.

It is another objective of the invention to provide means which present reduced impact on environment, as well as to provide electric energy economy directed to the metal casting.

BRIEF DESCRIPTION OF THE INVENTION

As the processes adopted in the industries of this branch, the labeling of cans comprise a first step in which the ink is applied on the surface by typographical process such as off-set of the like, followed by the passage of such cans through furnaces to provide the cure of the ink by heat. Such cure results in a strong adhesion of the ink to the metal, which is necessary in view of the conditions of use of the cans, that comprise, besides the handling to which they are subjected during commercialization and consumption, the contact with the moisture arising from cooling, etc.

In the proposed process, the aforementioned objectives, as well as other ones, are reached through the removal of printing before curing the ink, by means of application of a liquid that removes ink associated with friction by non-abrasive means.

According to another characteristic of the invention, the ink remover liquid consists of an alkaline aqueous solution.

According to another characteristic of the invention, the pH of the solution is equal or greater than 9.

According to another characteristic of the invention, the remover liquid may consist of an oil-in-water dispersion.

According to another characteristic of the invention, said friction is provided by means of the relative movement between the printed surface of the metal and a non-abrasive frictioning cushion.

According to another characteristic of the invention, said friction is associated to the application of the remover liquid.

According to a preferred embodiment of the invention, the remover liquid comprises an alkaline aqueous solution.

According to a more preferred embodiment of the invention, the remover liquid consists of a sodium hydroxide alkaline aqueous solution.

According to another characteristic of the invention, in a preferred embodiment in which the cans have cylindrical shape, said friction is provided by the contact of a cushion with the can surface to which it is produced a rotation movement around the longitudinal axis thereof.

According to another characteristic of the invention, the equipment employed comprises at least one rotating mandrel, in which the can is temporarily engaged and retained during the friction operation.

According to another characteristic of the invention, the retention of the can in said mandrel is preferably provided by means of vacuum or even by equivalent means.

According to another characteristic of the invention, a detector capable of identifying the presence of printing waste can be coupled to said equipment.

DESCRIPTION OF THE FIGURE

The other advantages and characteristics of the invention will become more evident from the description of a preferred embodiment, provided by way of example and not in a sense of limitation, and from the single FIGURE related thereto, in which it is depicted the equipment as well as the process proposed herein.

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is to provide the cleansing conditioning cans for drinks, food and other applications in general, wherein possible printing errors have occurred in the body thereof. The said object is reached by means of a process in which the ink is removed before the cure thereof, by remover liquid spray and non-abrasive friction. The remover liquid employed is preferably an alkaline solution having a pH equal or greater than 9; advantageously, this liquid consists in a solution of sodium hydroxide in water, in a concentration ranging from 0.1% to 1.5% of NaOH, it being preferred a concentration of about 0.2% NaOH, nevertheless, other substances that are appropriate to the proposed end may be used. Said spray may be carried out in one or more steps, wherein at least one of them is associated to friction of the printed surface by means of a cushion of soft and non-abrasive material. In the depicted exemplifying embodiment, three spray steps are used, wherein the two last ones are followed by friction.

According to the principles of the invention, the equipment used in the process comprises means that supports the can in appropriate position, besides providing the rotation of the can around the longitudinal axis thereof, non-abrasive friction means in contact with the side printed surface of the can during said rotation and spray means of the remover liquid on this surface during said friction. In a practical accomplishment manner of the invention, said supporting means are provided by cylindrical mandrels having a diameter lightly lower than the inner diameter of the cans, which are engaged thereto through axial sliding. Said mandrels are associated to mechanisms that produce rotation around the axles thereof. Due to the provision of temporary retention means, the cans engaged therein solidarily spin with the mandrels, thereby providing the sliding contact of the printed surface with said friction means. The combined action of the sliding and the solvent liquid provides the removal of ink from the surface of the cans, without affecting the polished finishing of the surface, and allowing that, after washing and drying, these cans can be directed to the production line. Despite said mandrels can present the axles thereof arranged in any position, vertical or horizontal, it is preferably adopted the horizontal orientation, since it makes easier the engagement and disengagement of the cans. The treatment of the cans is carried out by a main equipment which comprises the following essential elements:

a) at least one mandrel comprising means of rotation around the axis thereof;

b) means for sliding insertion of the cans, one at a time, in the mandrels;

c) means for retaining the can in the mandrel after the sliding insertion thereof;

d) at least one element for spraying the ink remover liquid;

e) at least one soft non-abrasive friction element associated to means for the juxtaposition thereof to the printed surface of the can inserted in the rotating mandrel;

f) means for removing the can from the mandrel after the printing removal.

Complementarily, the system comprises accessory means, the first of them conducting the printed cans up to the printing removal equipment and the second one providing the washing of the already treated cans and directing them back to the production line.

An advantageous form of accomplishing the invention which improves the efficiency of the process consists in using a plurality of mandrels, regularly placed in the edge of a rotating base that moves in increments equal to the angular distance between said mandrels, with pauses between the successive displacements. Such accomplishment allows that some of the above-mentioned elements, such as (b), (d), (e) and (f), can be installed in distinct positions, in order to enable the simultaneous execution of several steps of the process. More specifically, such elements are placed in positions coinciding with those of the cans in the pause points between said displacements.

FIG. 1 depicts a form of accomplishment of the invention in which said main device 10 comprises six mandrels 11 having the axles horizontally arranged, equidistantly arranged along the edge of a vertical disk-shaped round plate 12, the angle α between the adjacent mandrels being equal to 60°. The incremental displacement of disk 12 are, therefore, equal to 60°, that is, ⅙ of circumference, the pause points being designated in the FIGURE as I, II, III, IV, V and VI. As shown in the FIGURE, the cans are conducted up to said device through a gutter 13, wherein the cans to be treated are positioned in parallel among each other and perpendicularly to the displacement direction indicated by arrow 15. Above position 16 in said gutter, there are provided means for momentarily retaining each can, the can being sprayed with a solvent liquid applied by a first sprinkler 17. Then, the can slids through the most inclined portion 18 of the gutter, achieving a positioning element 19 which arranges the can 14 b in a position corresponding to the pause point I of the disk, said can being in alignment with mandrel 11.

As illustrated in the FIGURE, the means that produce the sliding insertion of the can onto the mandrel consist of a piston 21 located in this position, which pushes the can so that it externally engages in the mandrel. The piston drive is made through known means, such as compressed air or the like. After the engagement, the can is retained in the mandrel by means of vacuum application, through known means which have not been illustrated in the FIGURE. As previously mentioned, the mandrel rotates around the longitudinal axis thereof, said rotation being provided by known means that have not been detailed in the FIGURE.

After two successive displacements of 60°, the can 14 c engaged in the mandrel reaches position III, where it is subjected to a first ink removal operation, through spray with the remover liquid, it being concomitantly rubbed by the soft cushion 22, of which approach and removal from the can surface are controlled by piston 23, which is driven by known means, such as compressed air or the like. More precisely, the resting position of cushion 22 is that illustrated in the FIGURE, that is, away from the can. Immediately after the can 14 c is in position III, piston 23 is driven, approaching the soft cushion 22 to the surface of the rounding can until it is contact thereto, the can being continuously sprayed by the remover liquid from spray 24. At the end of the pause period of the disk, the cushion 22 is removed from the can, and the can is displaced up to position IV, where spray and friction occur again, through the sprinkler 25 and the cushion, which is constituted by the soft sponge 26. At the end of this second step of removing printing ink, the disk is subjected to more two displacements of ⅙ back, leading the can to positions V and VI. When the can 14 e reaches position VI, it is expelled from mandrel 11 b by means of compressed air application, it being directed to a washing and conveying system back to the production line (not illustrated).

Even though the invention has been described based on a specific exemplifying concretization, it is understood that modifications can be introduced in said apparatus without exceeding the conceptual limits of the invention. Thus, for example, the main equipment 10 can be provided from a different number of mandrels, such as 3, 4, 5 or more mandrels, being within the inventive concept. Likewise, the support plate 12 may be polygonal (triangular, square, pentagonal, hexagonal, etc.), instead of circular as illustrated. Furthermore, the number of sprinklers or sponges can be different from that illustrated in the FIGURE. Moreover, the relative movement between the printed surface and the soft cushion can be obtained by keeping the can motionless and moving the cushion along it, such option being more functional in the case of cans having non-circular sections, such as oblong, elliptical or prismatic.

Accordingly, the invention is described and delimited by the set of claims that follows. 

1. Process for removing printing in metallic packages of drinks, food and other applications in general, characterized by comprising the removal of ink before the cure thereof, by means of spray with ink remover liquid and non-abrasive friction.
 2. Process, according to claim 1, characterized in that said remover liquid consists of an alkaline aqueous solution.
 3. Process, according to claim 2, characterized in that said solution has a pH equal or greater than
 9. 4. Process, according to claim 3, characterized in that said solution consists in a solution of sodium hydroxide in water.
 5. Process, according to claim 4, characterized in that the concentration of said solution is comprised between 0.1% and 1.5% by weight of NaOH.
 6. Process, according to claim 5, characterized in that the concentration of said solution is of about 0.2% by weight of NaOH.
 7. Process, according to any of the previous claims, characterized by comprising at least one step of spray with ink remover liquid simultaneously with the friction of the printed surface by a soft and non-abrasive element.
 8. Process, according to claim 7, characterized in that said friction is provided by means of the relative displacement between the printed surface and said soft and non-abrasive element in contact with said surface.
 9. Process, according to claim 8, characterized in that said relative displacement is provided by moving the printed surface, the said soft and non-abrasive element keeping motionless.
 10. Process, according to claim 8, characterized in that said movement of the relative displacement is provided by moving the soft and non-abrasive element, the said printed surface keeping motionless.
 11. Process, according to claim 9, characterized in that said relative displacement of the printed surface is provided by the rotation of said package around the longitudinal axis thereof.
 12. System for removing printing in metallic packages of drinks, food and other applications in general, characterized by comprising a main equipment, consisting of the following elements: at least one mandrel which spins around the axis thereof, it having a diameter lightly lower than that of the package to be treated and comprising means for the retention thereof; propulsion means of each single package for the engagement thereof in the at least one mandrel; means for temporally retaining each package after said engagement in the at least one mandrel; means for spraying an ink remover liquid onto the package surface engaged in the mandrel and presenting rotation movement around the axis thereof; means of sliding juxtaposition of a soft and non-abrasive element to the surface of said package; means for removing the can from the at least one mandrel after the end of the ink remover liquid spray combined with the juxtaposition of said soft and non-abrasive element.
 13. System, according to claim 12, characterized in that said package consists in a can.
 14. System, according to claim 13, characterized in that said package consists in a can for drinks.
 15. System, according to claim 12, characterized by comprising a set of mandrels mounted on a rotative base which is displaced in angular increments that are equal to the angular distance between said mandrels, with pauses between successive displacements.
 16. System, according to claim 15, characterized by being provided, in at least one of the positions corresponding to one of said pauses, of means for spraying an ink remover liquid onto the package surface and/or means of sliding juxtaposition of a soft and non-abrasive element to the surface of said package.
 17. System, according to claim 12 or 15, characterized in that said propulsion means of each said package consist of a piston driven by compressed air or the like.
 18. System, according to claim 12, characterized in that said spray means are provided by a sprinkler.
 19. System, according to claim 12 or 15, characterized in that said temporarily retention means of said package in the mandrel are provided by vacuum application or even by equivalent means.
 20. System, according to claim 12 or 15, characterized in that said means for removing said package are provided by compressed air.
 21. System, according to claim 12, characterized by additionally comprising a sprinkler equipment placed in a feeding gutter of said packages before the processing thereof by said main equipment. 